1. Field of the Invention
The present invention relates to a target for a laser cathode ray tube (CRT) with improved efficiency by improving an adhesion layer for adhering a laser projecting portion and a radiation layer to each other, and a fabrication method thereof.
2. Description of the Related Art
In general, a conventional laser CRT includes a tube in which an electron gun is installed, a bulb integrally welded with the tube and a target portion for generating a laser beam by collision of electron beams emitted from the electron gun.
FIG. 1 shows a target 10 for a conventional laser CRT, including a laser projecting portion 11, a radiation layer 12 and an adhesion layer 15.
The laser projecting portion 11 is comprised of a semiconductor layer 13 made of a single crystal such as CdS, CdSSe or ZnSe, and first and second mirrors 14a and 14b respectively fixed on the bottom and top surfaces of the semiconductor layer 13. The radiation layer 12 is made of sapphire so that the heat generated from the laser projecting portion 11 is conducted and emanated.
The first mirror 14a of the laser projecting portion 11 is adhered to the radiation layer 12 by the adhesion layer 15. Here, the adhesion layer 15 serves to transmit the heat generated from the laser projecting portion 11 to the radiation layer 12 and acts as a buffer layer when polishing a surface of the semiconductor layer 13. Also, the adhesion layer 15 maintains the flatness of the laser projecting portion 11 during the polishing process. A laser generated from the laser projecting portion 11 is transmitted through the adhesion layer 15.
During the operation of the conventional laser CRT, when a voltage is applied to an electron gun (not shown), an electron beam is emitted from the electron gun to the laser projecting portion 11. The electron beam impinges on the semiconductor layer 13 to thus excite electrons, thereby generating light. The generated light resonates between the first and second mirrors 14a and 14b and is emitted as a laser beam. Then, the laser beam penetrates the radiation layer 12 and is projected onto a screen through a lens (not shown).
Here, the heat generated from the semiconductor layer 13 is conducted to the radiation layer 12 through the adhesion layer 15 to then be emitted to the outside. Conventionally, transparent epoxy glue having a shear stress of 1 Kg per unit area, has been used as the adhesion layer 15. The adhesiveness and light transmittance of the optical glue tend to be noticeably reduced at a temperature of 150.degree. C. or higher. Thus, the processing or driving temperature at which the laser CRT is driven is limited to the range of -200.about.150.degree. C.
During fabrication of a laser CRT, the inside of the laser CRT must be maintained at a high-vacuum state while being applied to a high-temperature furnace. However, since the upper limit temperature is limited to the above temperature range, it is rather difficult to achieve a high-vacuum state.
Also, while a laser CRT is driven, since an adhesion layer cannot withstand heat immediately applied by electrons at a high voltage, the degree of the vacuum state of a bulb is lowered.